Mobile telecommunication systems include wireless links between mobile stations (MS), which may be mobile telephones, pagers, computers, etc., and a base station (BS) of the mobile telecommunication system. Since these links are wireless, the links are susceptible to noise and interference with other signals. The signals received at the mobile station or at the base station may fade due to errors in the RF links or legs coupling the base station to the mobile station. That is, the data signals received by the mobile station may become much more attenuated than the surrounding noise and other interference.
The quality of wireless telecommunication is often measured by the ability of the mobile station to receive accurate and clear data from the base station. As errors are detected by the mobile station, the base station may increase the transmission power on the leg that couples the base station and the mobile station. When greater power is used on a RF link or leg, the power increase causes interference for other links or legs coupling the base station to other mobile stations and with other links from other base stations coupling to the mobile station in a soft handoff configuration.
When the RF links, or legs, between the mobile station and a base station becomes weak, for example, a hill might interfere with line-of-sight transmission, typical base station equipment tends to rapidly drive up the weak leg or link to full power. This creates several problems. The first being that since the base station has a finite amount of power, using excessive power in any one link will necessarily limit the power available for links with other mobile stations. Second, excessive use of power by base station creates more RF interference for other mobile stations in the area.
In real RF conditions, aspects such as link imbalance can cause errors in fast forward power control information received from the mobile station, which can cause the BS to ramp up to excessive transmit power, particularly in soft handoff conditions. Deep fades or momentary RF blocking can also cause the mobile station to overshoot its target signal-to-noise ratio setpoint, further exacerbating the problem. Both of these cause the BS to ramp up its transmit power far in excess of what is required. The prior art has static setpoints for maximum transmit power from the base station and maximum signal-to-noise ratio setpoint for the mobile station. Therefore, the prior art is unable to efficiently cope with errors in fast forward power control information and deep fades.
Accordingly, it would be highly desirable to have method of adjusting maximum and minimum BS transmit power boundaries in a wireless communication system.
Elements in the Figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the Figures may be exaggerated relative to other elements to help improve understanding of various embodiments of the present invention. Furthermore, the terms “first”, “second”, and the like herein, if any, are used inter alia for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. Moreover, the terms “front”, “back”, “top”, “bottom”, “over”, “under”, and the like in the Description and/or in the Claims, if any, are generally employed for descriptive purposes and not necessarily for comprehensively describing exclusive relative position. Any of the preceding terms so used may be interchanged under appropriate circumstances such that various embodiments of the invention described herein may be capable of operation in other configurations and/or orientations than those explicitly illustrated or otherwise described.